Soil is a complex medium that includes a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. In agriculture, horticulture, or gardening, it is often desirable to use land that is not initially optimal for growing plants. To that end, soil amendment compositions and fertilizers have been developed for optimizing the soil for plant growth.
While both are important, soil amendment compositions are different from fertilizers. Unlike fertilizers, which have the primary goal of adding nutrients to soil, soil amendment compositions can modify the condition of the soil itself. Fertilizers impact plant growth directly, while soil amendment compositions affect growth indirectly and sometimes deliver nutrients as a bonus. The goals of soil amendment compositions include improving soil's physical properties, such as water retention, permeability, water infiltration, drainage, aeration and structure.